Pulling Neutral at Speed

You can do this to rev while moving. Pull the up paddle to engage, the computer will select the applicable gear.

 

When you're in neutral and rolling then pull a paddle, the system will choose the correct gear. If that was not the case and you did this at 150 kph, then hit first, you would wreck the drive train if not the car.

 

Exactly. With one exception. I have found that no matter which paddle is pulled, the TXU selects one gear too high for my liking. So, when I do this, I pull the downshift paddle, so that my fingers are there and ready for a quick downshift to the gear I want.

Personal preference, really, but that's how I do it.

 

One or even two too high. Same behavior as the old F1's (my 430, e.g.). Seems the software specifically selects a conservative gear (probably the same gear it would be in if you were in Auto mode).

 

Now that's sorted; why would you do such a thing?

 

Now that is a good question! I can't think of any situation where I would do this.

 

Easy. Had to do it when I heard a noise and wanted to see if it was engine speed related, wheel speed related or something else... Turned out it was a wheel bearing...

SV

 

I do it approaching red lights. Drop into neutral to slow down and stop on the red, but if the light changes before I get there, pop it back in gear and off I go.

 

BTDT, just never had to worry about this in a computer-shift manual car.

 

When you shift into neutral in any gear while in motion, the (forward) shear forces exerted by the driveline on your tires' contact patches should dramatically lower, reducing the likelihood of loss of traction if the conditions are marginal for grip or if you car is already skidding. This improves traction at the contact patches, at the expense of acceleration and speed.

The reason why Ferrari's designers place the DCT in a "higher gear than some people's liking" is probably because they want to avoid abrupt changes in shear forces on the contact patches when the driveline re-engages. This could result in unintentional "engine braking". Unintentional or clumsy application of engine braking can cause a sudden loss of steering control under marginal road conditions.

The Ferrari engineers cannot predict the condition of the road surface in front of your wheels when you re-engage the driveline while the car is in motion.

 

Good explanation. To add a few fine points (I.e. overkill)

1) when coasting at neutral at speed, generally speaking the deceleration is primarily aerodynamic at relatively higher speeds (>50mph, though every car is different), followed by driveline losses, followed by rolling resistance on the tires (which is relatively minuscule)

2) an earlier poster was correct, when you engage N at speed, then re-engage a gear, the ECU defaults "high", though the car knows exactly how fast it's going and could easily match revs to a lower gear. Seems to be identical to the shift map for Auto mode, but as stated, the primary reason is to minimize loading

3) as a practical example, if you are in a manual shift car going quickly, pop it into neutral, then drop a gear and dump the clutch, without a blip you will load up the rear wheels...which may cause the chassis to get unstable. Shift a gear higher, and almost nothing happens. It's primarily a safety-drive piece of logic. DCT is the same (as programmed), just does it automatically.

4) I usually only pull N while driving so I can rev the engine up when I'm passing by my friend's house. Usually at 11pm or 4am. But that's me. Generally speaking, there is no good reason to pull neutral while driving (unless you want to listen for non-engine related drivetrain noise). Once did a "homework assignment" with my daughter on aerodynamics, she videotaped me doing "coast downs" from 70, 50, 30 and 10mph. We also did in the race car; with a big wing and splitter, when you pull N at 160mph, you go for a long distance, but you can feel the negative G in your harness until the speed gets below 60 or so.

 

Yeah, when a car is going "at speed" it's pretty hard to see how engaging neutral would be useful (from the perspective of a speeding Fcar). However, from my own experience there is one situation where neutral might be useful.

Say you are driving at speed and suddenly feel the tires starting to lose traction as you find yourself going over a long stretch of slippery ground ...and there's a corner coming up.

You worry you might actually lose steering control if you touch the brakes or if you even reduce throttle. In that situation, it might be safer to engage neutral and then re-engage to a gear that feels a bit "high" as the car slows and regains full traction. Engaging neutral is like reducing throttle but without the risk of unintended braking effects from engine and transmission drag. There is still driveline drag, rolling resistance and aerodynamic drag but the engine and (most of the) transmission are disengaged so the risk of unintended braking is greatly reduced.

When I drove BMWs with manual transmissions I did sometimes engage neutral to recover from loss of traction in tricky corners under street legal speeds, but never "at speed". I can't vouch for current models but older BMWs tended to be tail-happy in corners and this "engage neutral" maneuver was something an experienced manual transmission BMW owner needed to be familiar with, especially in northern climes.